The influence of SiC and Al2O3 micrometric particles on the electrodeposition of ZnNi films and the obtainment of ZnNi–SiC and ZnNi–Al2O3 electrocomposite coatings from slightly acidic solutions

In this work it was studied the influence of micrometric SiC and Al2O3 ceramic particles on the electrodeposition of ZnNi films from a moderately acid solution. At the same time, the possibilities of obtainment of ZnNi–SiC and ZnNi–Al2O3 electrocomposites were demonstrated. In the first part, it will be analyzed the effects of SiC and Al2O3 on the individual electrodeposition curves for Zn, Ni and on ZnNi films and on the hydrogen evolution reaction (HER). Both, SiC and Al2O3, causes the current densities in the electrodeposition curves of Zn, Ni and ZnNi to be increased. This was attributed to an additional mass-transport component to the electrode surface given by the flux of impinging particles to it. This makes the deposited quantities to be increased during the potentiodynamic sweeps. Regarding HER, in the blank solution, on a pure Zn substrate, SiC causes an increase on HER and Al2O3 has negligible effects on it. In the second part, it will be shown that it was possible to obtain ZnNi–SiC and ZnNi–Al2O3 electrocomposites. The compositional analysis of the films showed that the ZnNi electrodeposition is anomalous for the whole analyzed range and for all the systems. However, it was verified that, while, Al2O3 has practically no effects on the [Ni/Zn] ratio of the metal matrix, compared to pure ZnNi films, SiC promotes a decrease in this relation, directly related to its concentration in the solution. SiC augmented the anomalous behavior. Considering the high Zn content in electrodeposited ZnNi there would be the favoring of HER by SiC in these cases. There would be more favorable conditions for the formation of insoluble Zn(OH)2 at the electrode surface. The hindering in the Ni2+ reduction will be more effective and could explain the decrease in [Ni/Zn].